The present invention relates to a ball grid array (hereinafter referred to as BGA) module using a built-up circuit board and a method of manufacturing the module. More particularly, it relates to a BGA module having a solder ball structure positioned thereon to make electrical and mechanical connections with a circuit card.
As recent high density and high integration advances in ultra large scale integrated circuits (ULSI) have been made, BGA packages are becoming more mainstream in surface mount technology as the solder ball chip connection (SBCC) of choice, superseding conventional surface mount packaging component connections.
A substrate adapted to package a high density and highly integrated flip chip having a terminal BGA connection has low parasitic capacitance and inductance, yielding superior electrical characteristics. BGA packaging is very desirable when a high density package utilizing a tightly spaced contact array of solder joints is needed.
A BGA module can have an electrical structure positioned on the top and/or the bottom surface of a substrate made of a dielectric material such as a ceramic or a plastic. In a structure such as this, contact pads of at least one semiconductor chip and a plurality of solder balls are aligned with the electrical structures on the top and/or bottom surfaces of the substrate and reflowed to make electrical interconnections. FIG. 9 shows an enlarged cross-sectional view in elevation of a portion of a conventional BGA module 100 with a solder ball 102 mounted on a BGA pad 104 before reflow. Solder resist 106 is provided to separate solder ball 102 from a matrix of other solder balls (not shown) during reflow. The thickness of the solder resist is usually about 10 to 20 xcexcm. When solder ball 102 is mounted on BGA pad 104 before reflow using flux, there is a possibility that the solder ball may become dislodged from the BGA pad in the reflow process. More particularly, the mounted solder ball can become dislodged from the BGA pad above and beyond the height of the solder resist by vibrations of the reflow oven conveyor or by the thermal stress generated when the flux is softened. The loss of only one solder ball, for any of the above reasons, is an imperfection in electrical continuity in the BGA module and is a defect.
A variety of techniques can be utilized to keep solder balls from dislodging from the BGA pads during reflow. For example, holding jigs used for arranging solder balls on BGA pads can be employed to hold the solder balls during reflow. Also high viscosity flux in conjunction with solder paste can be applied onto the BGA pads on which the solder balls are arranged to hold the solder balls before and during the reflow process.
When jigs are used, however, a process for arranging jigs is required. On the other hand, when flux is used, a process for applying and removing flux is required. In addition, when solder paste is used, an applying process is required.
The present invention is directed at overcoming the problems set forth above. It is desirable to have a method of making a BGA module that keeps solder balls from becoming dislodged during the process of manufacturing the BGA module.
Accordingly it is an object of this invention to enhance the art of packaging technology.
It is another object of this invention to provide a novel method for producing a ball grid array module for mounting a semiconductor chip and a solder ball thereon.
It is another object of this invention to provide a ball grid array module that will be manufactured with increased yields and can be produced at relatively lower costs than many current products.
Still another object of this invention is to provide a ball grid array module having a surface for mounting a semiconductor chip or the like and a solder ball thereon. The module includes a cavity for having the solder ball positioned therein that prevents dislodgment of the solder ball during heating of the module, resulting in much lower defect levels.
According to one aspect of the invention, there is provided ball grid array module having a surface for mounting a semiconductor chip and a solder ball. The ball grid array module includes a substrate having an upper surface, a first insulation layer including a first layer of circuitry therein positioned on the upper surface of the substrate, a second insulation layer including a second layer of circuitry therein positioned on the first insulation layer, and at least one internal side wall defining a cavity in the first and second insulation layers and having a bottom wall defined by the upper surface of the substrate, the bottom wall adapted for having the solder ball positioned thereon.
According to another aspect of the invention, there is provided a method of manufacturing a ball grid array module having a surface for mounting a solder ball. The method comprises the steps of providing a substrate having an upper surface, positioning a first insulation layer including a first layer of circuitry therein on the upper surface of the substrate, positioning a second insulation layer including a second layer of circuitry therein on the first insulation layer, and forming at least one internal side wall defining a cavity in the first and second insulation layers and having a bottom wall defined by the upper surface of the substrate, the bottom wall adapted for having the solder ball positioned thereon.